Atoms and nuclei. The atom helium (He) consists of two protons, two neutrons, and two electrons. (Recall that density is mass divided by volume, and consult Appendices A and E and Table 1.1 as needed.) (a) The diameter at the He atom is approximately 0.10 nm. Calculate the density of the He atom in g/cm- (assuming that it is a sphere), and compare it with that of pure water, which is 1.0 g/cm3 (b) The diameter of the He nucleus is about 2.0 fm Assuming the nucleus to be a sphere, calculate its density in g/cm’ and compare it with that of a neutron star in Problem 16.
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